In recent years, in order to suppress electromagnetic induction noise generated by an electric apparatus and to reduce a switching loss of switching devices, studies of low loss and low noise have been done to which soft switching techniques for performing zero voltage switching (ZVS) or zero current switching (ZCS) on switching devices are applied. Even in a DC/DC converter, the soft switching technology is applied, and characteristics of the DC/DC converter have been improved.
As an example of circuit system of the DC/DC converter to which the soft switching is applied, there is a phase shift PWM (Pulse Width Modulation) control method. A conventional example of phase-shift PWM controlled DC/DC converter to which the soft switching is applied is disclosed, for example, in Patent Document 1.